Semiconductor device

Abstract

To provide a semiconductor device capable of reducing oxygen deficiency in a metal oxide, and of stabilizing electrical characteristics.SOLUTION: A semiconductor device comprises: a gate electrode; a gate insulating film provided on the gate electrode; a first metal oxide film provided on the gate insulating film; a source electrode and a drain electrode provided so as to be contacted with the first metal oxide film; and a passivation film provided on the source electrode and the drain electrode. The passivation film is configured by sequentially laminating a first insulating film, a second metal oxide film, and a second insulating film.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a semiconductor device using an oxide semiconductor.

[0002] In this specification, a semiconductor device is a device that can function by utilizing semiconductor characteristics. In this specification, a transistor refers to a semiconductor device, and an electric device including the transistor Optical devices, semiconductor circuits, and electronic devices are all included in the category of semiconductor devices. [Background technology]

[0003] It is used in many flat panel displays, such as liquid crystal displays and light-emitting displays. The transistors used are made of amorphous silicon and single-crystal silicon formed on a glass substrate. It is made of a silicon semiconductor such as silicon or polycrystalline silicon. Transistors using silicon semiconductors are also used in integrated circuits (ICs).

[0004] A technology that uses metal oxides that exhibit semiconductor properties in transistors instead of the silicon semiconductors mentioned above. In this specification, metal oxides that exhibit semiconducting properties are referred to as "oxide semiconductors." For example, oxide semiconductors include Zn-O oxides and In-Ga-Z A transistor is manufactured using an nO-based oxide, and the transistor is used as a switch for a pixel of a display device. Techniques for use in etching elements and the like have been disclosed (see Patent Documents 1 and 2). ).

[0005] Incidentally, it has been pointed out that hydrogen is a carrier supply source in oxide semiconductors. Therefore, it is necessary to take measures to prevent hydrogen from being mixed in when forming the oxide semiconductor. In addition, hydrogen in the oxide semiconductor and the gate insulating film in contact with the oxide semiconductor can be reduced. By reducing the number of gates, the fluctuation of the threshold voltage is reduced (see Patent Document 3). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-123861 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-96055 [Patent Document 3] Japanese Patent Application Laid-Open No. 2009-224479 Summary of the Invention [Problem to be solved by the invention]

[0007] Furthermore, in metal oxides, the carrier source is not only hydrogen but also oxygen vacancies in the metal oxide. Some of the oxygen vacancies in the metal oxide become donors, and oxygen is released into the metal oxide. The electrons that are carriers are generated by oxygen in the metal oxide that contains the channel formation region of the transistor. If there are many defects, electrons are generated in the channel formation region, and the transistor This causes the threshold voltage to shift in the negative direction.

[0008] In addition, an insulating film provided in contact with the metal oxide film including the channel formation region can also The threshold voltage of the transistor is affected by negative ions such as oxygen ions of unbonded oxygen. The fixed charge contained in the insulating film causes a positive shift in the threshold voltage of the transistor. However, if oxygen is released from the insulating film to the outside, The negative fixed charge decreases, causing the threshold voltage of the transistor to shift in the negative direction. There is a risk of this happening.

[0009] Therefore, one embodiment of the present invention is to reduce oxygen vacancies in a metal oxide including a channel formation region, In addition, oxygen contained in the insulating film in contact with the metal oxide is prevented from being released to the outside. Therefore, an object of the present invention is to provide a semiconductor device having good and stable electrical characteristics. It shall be one of the following. [Means for solving the problem]

[0010] In a transistor using a metal oxide, in order to reduce oxygen vacancies in the metal oxide, Therefore, in one embodiment of the present invention, a channel An insulating film from which oxygen is released by heat treatment is provided in contact with the metal oxide film including the hole formation region. As a result, oxygen released during the heat treatment is supplied to the metal oxide, filling the oxygen vacancies. can be reduced.

[0011] In addition, the insulating film (also referred to as the first insulating film) from which oxygen is released by heat treatment The oxygen diffuses outward, so there are cases where the metal oxide cannot be supplied with enough oxygen. Therefore, in one embodiment of the present invention, a chalcogenide film is formed in contact with an insulating film from which oxygen is released by heat treatment. A metal oxide film other than the metal oxide film (also referred to as the first metal oxide film) including the panel-forming region The second metal oxide film is a thin film having a high oxygen permeability. By providing the second metal oxide film, it is possible to prevent the formation of a thin film during heat treatment. The desorbed oxygen can be prevented from diffusing outward. It is possible to supply sufficient oxygen to the film, and the oxygen contained in the insulating film is not released to the outside. This can prevent this from happening.

[0012] In addition, oxygen deficiency may occur in the second metal oxide film that prevents oxygen from passing through. However, in one embodiment of the present invention, the second metal oxide film is subjected to a heat treatment to remove oxygen. Since it is sandwiched between insulating films (first insulating film and second insulating film), Therefore, oxygen vacancies in the second metal oxide film can be compensated for.

[0013] One aspect of the present invention is a gate electrode, a gate insulating film provided on the gate electrode, and a gate insulating film. A first metal oxide film is provided on the insulating film, and a solenoid is provided in contact with the first metal oxide film. a source electrode and a drain electrode, and a passivation film provided on the source electrode and the drain electrode. and a passivation film including a first insulating film, a second metal oxide film, and a second insulating film. The semiconductor device is formed by laminating a semiconductor layer and an insulating film in this order.

[0014] Another aspect of the present invention is a gate electrode, a gate insulating film provided on the gate electrode, and a gate insulating film provided on the gate electrode. a first metal oxide film provided on the insulating film; and a second metal oxide film provided in contact with the first metal oxide film. A source electrode and a drain electrode, and a passivation layer provided on the source electrode and the drain electrode. the gate insulating film is made of a second insulating film, a second metal oxide film, and a first The semiconductor device is a semiconductor device in which an insulating film is laminated in this order.

[0015] In each of the above configurations, the first insulating film is thicker than the second insulating film in the semiconductor device.

[0016] In another embodiment of the present invention, a semiconductor device includes a base insulating film and a a first metal oxide film, and a source electrode and a drain electrode provided in contact with the first metal oxide film; an electrode, a gate insulator provided on the first metal oxide film, the source electrode, and the drain electrode; a gate electrode provided on the first metal oxide film via a gate insulating film, The base insulating film is formed by laminating a first insulating film, a second metal oxide film, and a second insulating film in this order. do.

[0017] In another embodiment of the present invention, a semiconductor device includes a base insulating film and a a first metal oxide film, and a source electrode and a drain electrode provided in contact with the first metal oxide film; an electrode, a gate insulator provided on the first metal oxide film, the source electrode, and the drain electrode; a gate electrode provided on the first metal oxide film via a gate insulating film, The gate insulating film is formed by laminating a second insulating film, a second metal oxide film, and a first insulating film in this order. There are.

[0018] In each of the above configurations, the first insulating film is preferably thinner than the second insulating film.

[0019] In each of the above structures, the first metal oxide film is a semiconductor that is thicker than the second metal oxide film. It should be noted that a metal oxide film of about 5 nm can prevent oxygen from passing through. In addition, since the metal oxide film has a high relative dielectric constant, the metal oxide film including the channel formation region When using a metal oxide film as an external element, if the film is too thick, the parasitic capacitance may increase. Therefore, the thickness of the second metal oxide film is preferably 5 nm or more and 15 nm or less. I wish.

[0020] In each of the above structures, the first insulating film and the second insulating film are insulating films from which oxygen is released by heat treatment. It is preferred to use a velum.

[0021] In each of the above structures, the first metal oxide film and the second metal oxide film are made of In, Ga, Sn and Zn. In the above, an element contained in the first metal oxide film and an element contained in the second metal oxide film are For example, the first metal oxide film and the second metal oxide film may be the same or different. The metal oxide film may be made of an In-Ga-Zn-O material, or a first metal oxide film. The first metal oxide film is made of In-Ga-Zn-O material. Ga-Zn-ON based materials may also be used.

[0022] In addition, metal oxide films can be either conductive or semiconductive depending on the amount of hydrogen and oxygen vacancies. For example, the resistivity of a metal oxide film is determined by the amount of metal contained in the film. It changes depending on the amount of hydrogen and oxygen vacancies.

[0023] The insulating films sandwiching the metal oxide film are insulating films that do not release oxygen during heat treatment. When the metal oxide film is processed, it becomes an electrical conductor. When an insulating film that releases oxygen by heat treatment is used for both, the metal oxide film It becomes an electrical insulator. In terms of the resistivity of a metal oxide film, the resistivity is 10 [Ω·cm] or less. becomes a conductor with a resistivity of 1×10 8 If it is more than [Ω·cm], it becomes an insulator.

[0024] In order to make the first metal oxide film a semiconductor, the resistivity must be such that it becomes a conductor and the resistivity must be such that it becomes an insulator. The resistivity of the first metal oxide film is set to 10 [Ω·cm]. Exceeding 1×10 8 It is sufficient to form it so that the resistivity is less than [Ω·cm].

[0025] The first metal oxide film and the second metal oxide film may be amorphous or crystalline. For example, the first metal oxide film may be non-single crystalline. When viewed from the direction perpendicular to the ab plane of the crystal, the atomic arrangement is triangular, hexagonal, equilateral triangular, or equilateral hexagonal. When viewed from the direction perpendicular to the c-axis, the metal atoms are layered or the metal atoms and oxygen atoms are layered. It is preferable that the metal oxide contains a phase in which the metals are arranged in a layered form. CAAC-OS film: C Axis Aligned Crystallin e Oxide Semiconductor.

[0026] By using a CAAC-OS film as the first metal oxide film, it is possible to This suppresses fluctuations in the electrical characteristics of transistors due to the application of heat and bias, and The reliability of the device can be improved. [Effects of the Invention]

[0027] According to one embodiment of the present invention, oxygen vacancies in a metal oxide are reduced, and a metal oxide in contact with the metal oxide is By preventing the oxygen contained in the insulating film from being released to the outside, good electrical characteristics and Furthermore, a semiconductor device having stable electrical characteristics can be provided. [Brief explanation of the drawings]

[0028] [Figure 1] 1A and 1B are a top view and a cross-sectional view illustrating an example of a semiconductor device according to one embodiment of the present invention. [Figure 2] 1A and 1B are diagrams illustrating semiconductor devices according to one embodiment of the present invention. [Figure 3] 1A to 1C illustrate a method for manufacturing a semiconductor device according to one embodiment of the present invention. [Figure 4]1A and 1B are a top view and a cross-sectional view illustrating an example of a semiconductor device according to one embodiment of the present invention. [Figure 5] 1A and 1B are diagrams illustrating semiconductor devices according to one embodiment of the present invention. [Figure 6] 1A and 1B are a cross-sectional view and a circuit diagram illustrating an example of a semiconductor device according to one embodiment of the present invention. [Figure 7] FIG. 1 is a circuit diagram of a semiconductor device according to one embodiment of the present invention. [Figure 8] 1A to 1C illustrate a method for manufacturing a semiconductor device according to one embodiment of the present invention. [Figure 9] 1A and 1B are diagrams illustrating electronic devices. [Figure 10] FIG. [Figure 11] FIG. [Figure 12] FIG. [Figure 13] FIG. 1 shows the results of CV measurements. [Figure 14] FIG. 1 shows the results of CV measurements. [Figure 15] FIG. 1 shows the results of CV measurements. [Figure 16] Figure showing the results of TDS. [Figure 17] FIG. 10 is a diagram showing the structure of a sample according to Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0029] The embodiments of the present invention will be described in detail with reference to the drawings. and the like, without departing from the spirit and scope of the present invention. It will be readily apparent to those skilled in the art that various modifications can be made to the above. The present invention described below should not be construed as being limited to the description of the embodiment. In the configuration of the present invention, the same parts or parts having similar functions are denoted by the same reference numerals in different drawings. These are commonly used between the surfaces, and their repeated explanation will be omitted.

[0030] In each of the drawings described in this specification, the size of each component, the thickness of the film, or the area is not clearly indicated. The figures may be exaggerated for clarity and are not necessarily limited to that scale. .

[0031] In addition, terms such as first, second, and third used in this specification are used in order to avoid confusion of components. It is not intended to limit the number of items. The terms "second" or "third" can be used interchangeably to explain the present invention.

[0032] The functions of "source" and "drain" are used when the direction of current changes during circuit operation. Therefore, in this specification, the terms "source" and "drain" are used interchangeably. The terms may be used interchangeably.

[0033] (Embodiment 1) In this embodiment, a semiconductor device and a manufacturing method thereof according to one embodiment of the present invention will be described with reference to FIGS. This will be explained using FIGS.

[0034] <Configuration example of semiconductor device> FIG. 1 illustrates a plan view and a schematic diagram of a transistor 200 as an example of a semiconductor device according to one embodiment of the present invention. 1(A) is a plan view, and FIG. 1(B) and FIG. 1(C) are cross-sectional views. These are cross-sectional views taken along the lines A1-A2 and B1-B2 in FIG. In FIG. 1(A), in order to avoid complexity, some of the components of the transistor 200 (e.g., For example, gate insulating film 104 is omitted.

[0035] The transistor 200 shown in FIG. 1 includes a gate electrode 102 and a gate electrode 103 on a substrate 100. A gate insulating film 104 is provided on the gate insulating film 104. a metal oxide film 106a and a source electrode or a drain electrode provided in contact with the metal oxide film 106a; The metal oxide film 106a has a semiconductor characteristic. Therefore, it is also referred to as an oxide semiconductor.

[0036] The transistor 200 shown in FIG. 1 is a bottom-gate transistor. The top and drain electrodes 108a and 108b are in contact with the top surface of the metal oxide film 106a. The source and drain electrodes 108a and 108b are made of gold. It may have a bottom contact structure in contact with the lower surface of the metal oxide film 106a.

[0037] The region where the metal oxide film 106a and the gate electrode 102 overlap is a channel forming region. It works.

[0038] The metal oxide film 106a contains two or more elements selected from the group consisting of In, Ga, Sn, and Zn. The metal oxide has a band gap of 2 eV or more and less than 6 eV. Preferably, it is 2.5 eV or more and 5.5 eV or less, and more preferably, it is 3 eV or more and 5 eV or less. In this way, by using metal oxides with a wide band gap, 00 can reduce the off-state current.

[0039] Further, on the metal oxide film 106a and the source or drain electrodes 108a and 108b, A passivation film 110 is provided. The passivation film 110 is made of a metal oxide. In the transistor 200 shown in FIG. The oxidization film 110 includes an insulating film 112, a metal oxide film 114, and an insulating film 116. Here, the insulating film 112 and the insulating film 116 are insulating films from which oxygen is released by heat treatment. It is used.

[0040] In this specification, "oxygen is released by heat treatment" means that TDS (Thermal Desorption Desorption Spectroscopy (thermal desorption spectroscopy) analysis revealed that the acid The amount of oxygen desorbed (or released) converted to elementary atoms is 1.0 x 10 18 cm -3 That's all, I prefer 3.0 x 10 20 cm -3 In addition, "oxygen is released by heat treatment" means that "Does not desorb" means that the amount of oxygen desorbed (or released) converted to oxygen atoms in TDS analysis is 1. 0×10 18 cm -3 It means that it is less than.

[0041] The following describes a method for quantifying the amount of released oxygen by converting it into oxygen atoms using TDS analysis.

[0042] The amount of gas released during TDS analysis is proportional to the integral value of the ion intensity. The amount of desorbed gas is calculated from the ratio of the integrated value of the ion intensity measured to the reference value of the standard sample. The reference value of a standard sample is the value of the atomic density of a sample containing atoms at a predetermined density. is the ratio of the atomic density to the integral value of the ionic intensity corresponding to

[0043] For example, the TDS analysis results of a silicon wafer containing a specified density of hydrogen as a standard sample, and From the results of TDS analysis of the insulating film, the amount of oxygen molecules desorbed from the insulating film (N O2 ) is calculated using Equation 1. Here, all of the gases detected at mass number 32 obtained by TDS analysis are acids. It is assumed to be derived from an elementary molecule. There is CH3OH as an element with a mass number of 32, but the possibility of its existence is It is not considered here as it is too low. Also, the mass number of the oxygen atom, which is an isotope of the oxygen atom, is 17. The abundance ratio of oxygen molecules containing oxygen atoms with mass number 18 in nature is extremely small. It is not considered because it is a quantity.

[0044] N O2 =N H2 / S H2 ×S O2 ×α (Equation 1)

[0045] N H2 is the density converted value of hydrogen molecules desorbed from the standard sample. H2 is a standard test The integral value of the ion intensity when the sample is subjected to TDS analysis. H2 / S H2 Let's say S O2 is the integral value of the ion intensity when the insulating film is analyzed by TDS. α is a coefficient that affects the ion intensity in TDS analysis. For details, see Japanese Patent Application Laid-Open No. 6-275697. The numerical values ​​of the amount of oxygen released are as follows: Using a thermal desorption analyzer EMD-WA1000S / W manufactured by Electronic Science Corporation, 1×10 16 cm -3 This is the value measured using a silicon wafer containing hydrogen atoms. .

[0046] In addition, some of the oxygen is detected as oxygen atoms in TDS analysis. The ratio of the oxygen molecules can be calculated from the ionization rate of the oxygen molecules. Since the ionization rate of oxygen atoms is included in the calculation, the amount of oxygen atoms released can be estimated by evaluating the amount of oxygen molecules released. It can also be estimated.

[0047] In addition, N O2 is the amount of oxygen molecules released. In the case of an insulating film, when converted to oxygen atoms, The amount of oxygen released is twice the amount of oxygen molecules released.

[0048] An example of a film from which oxygen is released by heat treatment is silicon oxide (SiOx(x >2)). Silicon oxide with excess oxygen (SiOx(x>2)) is a silicon atom It contains more than twice the number of oxygen atoms per unit volume. The numbers of carbon atoms and oxygen atoms are values ​​measured by Rutherford backscattering spectroscopy.

[0049] The metal oxide film 106 a is provided between the gate insulating film 104 and the insulating film 112 . The insulating film 112 is an insulating film from which oxygen is released by heat treatment, and the gate insulating film 104 is In this case, an insulating film that does not release oxygen by heat treatment is used. Oxygen is released from 112 and supplied to the metal oxide film 106a.

[0050] In addition, the insulating film from which oxygen is released by heat treatment contains negatively charged oxygen ions such as unbonded oxygen. It contains a large amount of constant charge. It is in contact with the metal oxide film including the channel formation region and is formed by heat treatment. By providing an insulating film from which oxygen is released, the threshold voltage of the transistor can be shifted positively. This is preferable because it allows for

[0051] However, oxygen released from the insulating film during heat treatment diffuses outward, and the metal oxide In some cases, oxygen cannot be supplied to the film 106a sufficiently. By doing so, the negative fixed charges in the insulating film are reduced. As a result, the threshold voltage of the transistor may be shifted negatively.

[0052] Therefore, in one embodiment of the present invention, a metal oxide film 106a is formed on and in contact with the insulating film 112. The metal oxide film 114 is provided. The metal oxide film can prevent oxygen from passing through. Therefore, oxygen contained in the insulating film 112 is released and diffused outward during the heat treatment. This can prevent the following.

[0053] In addition, oxygen vacancies may occur in the metal oxide film 114. The metal oxide film 114 is formed by an insulating film (insulating film 112 and insulating film 11) from which oxygen is released by heat treatment. 6) and install it by sandwiching it.

[0054] Metal oxide films can prevent oxygen from passing through even when they are extremely thin, about 5 nm thick. In addition, since the metal oxide film has a high relative dielectric constant (for example, 15), When a metal oxide film other than the metal oxide film containing Therefore, the thickness of the metal oxide film 114 is set to 5 The thickness of the metal oxide film 114 is preferably 100 nm or more and 15 nm or less. By making it an extremely thin film, the metal oxide film 114 may not be used in part of the passivation film. In this case, a significant increase in parasitic capacitance can be prevented compared to the case where the parasitic capacitance is increased.

[0055] The metal oxide film 114 provided to prevent outward diffusion of oxygen is desorbed by heat treatment. By sandwiching the insulating film 112 and the insulating film 116, the insulating film 1 Oxygen is released from the insulating film 116 and supplied to the metal oxide film 114, thereby filling the oxygen vacancies. As a result, the metal oxide film 114 becomes insulating (exhibits insulating properties). Even when used as part of the passivation film 110, the transistor 200 Therefore, the electrical characteristics of the semiconductor device are not affected.

[0056] In order to efficiently supply oxygen to the metal oxide film 106a, The thickness of the insulating film 112 in contact with the metal oxide film 114 is thicker than the thickness of the insulating film 116 in contact with the metal oxide film 114. The thickness of the insulating film 112 and the insulating film 116 is preferably the same as that of the passivation film 110. The thickness may be appropriately set depending on the film thickness.

[0057] When a film from which oxygen is released by heat treatment is used as the insulating film 112, Oxygen is supplied to the metal oxide film 106a, and the interface between the insulating film 112 and the metal oxide film 106a is formed. Therefore, the charge generated due to the operation of the transistor 200 can be reduced. This can prevent the metal oxide film 106a from being trapped at the interface between the insulating film 112 and the metal oxide film 106a. The transistor 200 can be one with little deterioration in electrical characteristics.

[0058] Furthermore, by providing the metal oxide film 114 in contact with the insulating film 112, outward diffusion of oxygen can be prevented. Therefore, oxygen vacancies in the metal oxide film 106a including the channel formation region can be prevented. This allows for sufficient compensation. Furthermore, the negative fixed charges in the insulating film 112 can be reduced. This prevents the threshold voltage of the transistor from increasing as the negative fixed charge decreases. Therefore, it is possible to prevent the low voltage from shifting negatively.

[0059] The hydrogen concentration of the metal oxide film 106a and the metal oxide film 114 is 1×10 20 at oms / cm 3 Less than 1 × 10 19 atoms / cm 3 Below, more preferably 1×10 18 atoms / cm 3 The channel-shaped metal oxide film 106a is In the formed region, the hydrogen concentration is reduced, and the difference between before and after light irradiation and the BT (thermal The threshold voltage fluctuation is small before and after the bias stress test, so stable voltage is obtained. It is possible to make a transistor that has high reliability and has excellent thermal properties. The hydrogen concentration of the metal oxide film 114 used as an insulator is preferably as low as possible. stomach.

[0060] The metal oxide film 114 is made of In, Ga, Sn, and Zn, similarly to the metal oxide film 106a. The metal oxide film 114 is a metal oxide containing two or more elements selected from the above. The element contained in the metal oxide film 106a may be the same as or different from the element contained in the metal oxide film 106a. For example, the metal oxide film 106a and the metal oxide film 114 may be made of In—Ga Alternatively, a Zn-O-based material may be used as the metal oxide film 106a. As the metal oxide film 114, an In-Ga-Zn-ON material is used. It may be used.

[0061] <Application examples of semiconductor devices> 2A to 2C are cross-sectional views of transistors having different structures from the transistor 200. The structure is shown.

[0062] The transistor 210 shown in FIG. 2A includes a gate electrode 102, a gate electrode 103, a gate electrode 104, a gate electrode 105, a gate electrode 106, a gate electrode 107, a gate electrode 108, a gate electrode 109, a gate electrode 110, a gate electrode 111, a gate electrode 112, a gate electrode 113, a gate electrode 114, a gate electrode 115, a A gate insulating film 120 is provided on the electrode 102, and a metal film is provided on the gate insulating film 120. The oxide film 106a and the source electrode or the drain electrode provided in contact with the metal oxide film 106a. The electrode 108a and the electrode 108b are provided.

[0063] The difference between the transistor 200 and the transistor 210 is that the gate insulating film 120 has a The metal oxide film is provided to prevent outward diffusion of oxygen. The insulating film 120 has a three-layer structure consisting of an insulating film 122, a metal oxide film 124, and an insulating film 126. In addition, the metal oxide film 106a and the source and drain electrodes 108a and 108b are An insulating film 118 is provided on the insulating film 12 as a passivation film. 2. The insulating film 126 is made of an insulating material that releases oxygen by heat treatment. The film 118 is made of an insulating film that does not release oxygen when subjected to heat treatment.

[0064] In order to efficiently supply oxygen to the metal oxide film 106a, The insulating film 122 in contact with the metal oxide film 124 is preferably thicker than the insulating film 126 in contact with the metal oxide film 124. The thicknesses of the insulating films 122 and 126 are appropriately set depending on the thickness of the gate insulating film 120. In addition, if the metal oxide film 124 is at least 5 nm thick, oxygen can pass through it. Therefore, if the thickness is appropriately set according to the thickness of the gate insulating film 120, That's fine.

[0065] The transistor 220 shown in FIG. 2B includes a gate electrode 102, a gate electrode 103, a gate electrode 104, a gate electrode 105, a gate electrode 106, a gate electrode 107, a gate electrode 108, a gate electrode 109, a gate electrode 110, a gate electrode 111, a gate electrode 112, a gate electrode 113, a gate electrode 114, a gate electrode 115, a A gate insulating film 120 is provided on the electrode 102, and a metal film is provided on the gate insulating film 120. The oxide film 106a and the source electrode or the drain electrode provided in contact with the metal oxide film 106a. The metal oxide film 106a, the source electrode or the drain electrode 108b, and the metal oxide film 106a are A passivation film 110 is provided on the drain electrodes 108a and 108b.

[0066] In the transistor 220, the gate insulating film 120 and the passivation film 110 are For this purpose, the description of the transistor 200 and the transistor 210 can be taken into consideration. Detailed explanation will be omitted.

[0067] In addition, in the transistor 200, the transistor 210, and the transistor 220, The source or drain electrodes 108a and 108b are in contact with the upper surface of the metal oxide film 106a. The top contact structure has been described. The source or drain electrodes 108a and 108b are in contact with the bottom surface of the metal oxide film 106a. A top-contact structure can also be adopted. An example of a bottom-contact structure is shown in Figure 2(C). Shown below.

[0068] The transistor 230 shown in FIG. 2C includes a gate electrode 102 and a gate A gate insulating film 104 is provided on the electrode 102, and a semiconductor layer is provided on the gate insulating film 104. Source or drain electrodes 108a, 108b and source or drain electrode 108a and a metal oxide film 106a provided in contact with the metal oxide film 108b. A passivation film 110 is provided on the transistor 106a in the same manner as the transistor 200. do.

[0069] The passivation film 110 is provided so as to cover the entire metal oxide film 106a. Therefore, oxygen can be efficiently supplied to the metal oxide film 106a.

[0070] In addition, even in a transistor with a bottom contact structure, the gate insulating film contains oxygen and other impurities. A metal oxide film may be provided to prevent lateral diffusion, and a part of the gate insulating film and a passivation film may be provided. A metal oxide film may be provided on a part of the insulation film to prevent outward diffusion of oxygen.

[0071] As described above, in one embodiment of the present invention, a metal oxide film (first In order to reduce oxygen vacancies in the second metal oxide film, the second metal oxide film is subjected to a heat treatment in contact with the first metal oxide film. In addition, the insulating film (first insulating film) from which oxygen is released is provided. a second metal oxide film (second insulating film) that is different from the first metal oxide film and is in contact with the insulating film (first insulating film) that is connected to the first metal oxide film; Furthermore, the second metal oxide film is subjected to a heat treatment to remove oxygen. It is sandwiched between insulating films (first insulating film and second insulating film) that are spaced apart.

[0072] The insulating film 112 (or insulating film 122) from which oxygen is released by heating is treated with the metal oxide film 106 a and the metal oxide film 114 (or the metal oxide film 124). Oxygen desorbed from the insulating film 112 (or insulating film 122) during processing is released to the outside. This can prevent the oxygen deficiency in the metal oxide film 106a from occurring, and the oxygen deficiency in the metal oxide film 106a can be sufficiently compensated for. In addition, the negative fixed charges contained in the insulating film 112 (or insulating film 122) are prevented from decreasing. That is, according to one embodiment of the present invention, oxygen vacancies in the metal oxide film 106a can be reduced. and the insulating film 112 (or insulating film 122) in contact with the metal oxide film 106a. By preventing the oxygen contained in the material from being released to the outside, it has good electrical properties and Therefore, it is possible to provide a semiconductor device with stable electrical characteristics.

[0073] <Method for manufacturing semiconductor device> Next, as an example of a method for manufacturing a semiconductor device according to one embodiment of the present invention, The manufacturing method will be described with reference to FIG.

[0074] First, a conductive film applicable to a gate electrode is formed on a substrate 100, and then photolithography is performed. A resist mask is formed on the conductive film by a process, and the conductive film is The gate electrode 102 is then etched into a desired shape. A gate insulating film 104 is formed on the silicon substrate 102 (see FIG. 3(A)).

[0075] The substrate 100 may be a substrate having an insulating surface. For example, a glass substrate, Substrates such as ceramic substrates, quartz substrates, and sapphire substrates can be used. If it has an edge surface, it can be a single crystal semiconductor substrate such as silicon or silicon carbide, or a polycrystalline semiconductor Substrates, compound semiconductor substrates such as silicon germanium, and SOI substrates can also be used. It is possible to provide a semiconductor element on the substrate. There are no major limitations on the substrate that can be used, but it must have sufficient heat resistance to withstand subsequent heat treatment. In this embodiment, a glass substrate is used as the substrate 100.

[0076] A flexible substrate can also be used as the substrate 100. When a flexible substrate is used, the transistor may be directly fabricated on the flexible substrate, or may be fabricated on another substrate. The transistor 200 may be fabricated and then peeled off and transferred. In order to separate and transfer the semiconductor device to a conductive substrate, a separation layer and an insulating film are provided on the substrate. All you need to do is create a Diaster 200.

[0077] Conductive materials that can be used for the gate electrode 102 include aluminum, titanium, chromium, nickel, and the like. copper, yttrium, zirconium, molybdenum, silver, tantalum, or tungsten The gate electrode may be a metal or an alloy containing the metal as the main component. The conductive film applicable to the electrode 102 may have a single layer structure or a laminated structure using the above-mentioned conductive materials. For example, a single layer structure of an aluminum film containing silicon, or a layer formed on an aluminum film Two-layer structure with titanium film laminated, two-layer structure with titanium film laminated on tungsten film, copper-metal A two-layer structure consisting of a copper film laminated on a magnesium-aluminum alloy film, a titanium film, and the titanium A three-layer structure in which an aluminum film is layered on top of a titanium film, etc. In addition, transparent indium oxide and indium oxide containing tin oxide or zinc oxide are also available. A conductive material may also be used.

[0078] The conductive film applicable to the gate electrode 102 is formed by sputtering, plasma CVD, or the like. The film thickness is then formed to be 50 nm or more and 300 nm or less. A resist mask is formed on the conductive film, and the conductive film is then patterned using the resist mask. The resist mask is then etched to form the gate electrode 102. In addition to the photolithography process, inkjet methods, printing methods, etc. can be used as appropriate. The etching process can be performed by dry etching, wet etching, or Dry etching and wet etching can be combined. In this state, tungsten is formed as a conductive film with a film thickness of 150 nm by sputtering. do.

[0079] The gate insulating film 104 is made of silicon oxide, gallium oxide, aluminum oxide, or the like. Any oxide insulating film or nitride insulating film such as silicon nitride or aluminum nitride or silicon oxynitride, aluminum oxynitride, silicon nitride oxide, or the like In addition to the above materials, hafnium oxide, yttrium oxide, Thorium, hafnium silicate (HfSi x O y x>0, y>0), nitrogen is added Hafnium silicate (HfSiO x N y (x>0, y>0)), hafnium aluminate (HfAl x O y (x>0, y>0)), high-k materials such as The gate insulating film 104 may be formed of a single layer of the high-k material. Alternatively, the insulating film may be formed as a laminated structure with an insulating film made of the above materials.

[0080] The gate insulating film 104 is formed to a thickness of 5 nm or more by a sputtering method, a plasma CVD method, or the like. The gate insulating film 104 is formed to a thickness of 300 nm or less. By using this, the electrical thickness of the gate insulating film (e.g., silicon oxide film equivalent) can be changed. The physical gate insulating film can be made thicker without any problem, which reduces gate leakage current. It can be reduced.

[0081] In this embodiment, the gate insulating film 104 is formed by a silicon oxynitride film by a plasma CVD method. The silicon oxide film formed by the plasma CVD method is then heat treated to This is a film from which oxygen does not desorb.

[0082] Next, a metal oxide film 106 is formed on the gate insulating film 104 (see FIG. 3(B)).

[0083] The metal oxide film 106 is made of two or more materials selected from the group consisting of In, Ga, Zn, and Sn. For example, a metal oxide material containing In—Sn, which is a quaternary metal oxide, can be used. -Ga-Zn-O based materials and In-Ga-Zn-O based materials, which are ternary metal oxides, In-Sn-Zn-O based materials, In-Al-Zn-O based materials, Sn-Ga-Zn-O Materials based on Al-Ga-Zn-O, materials based on Sn-Al-Zn-O, and binary alloys Metal oxides such as In-Zn-O, Sn-Zn-O, and Al-Zn-O Materials, Zn-Mg-O based materials, Sn-Mg-O based materials, In-Mg-O based materials, I n-Ga-O based materials, In-O based materials, Sn-O based materials, Zn-O based materials, etc. Here, for example, the In-Ga-Zn-O based material is indium (I n), gallium (Ga), and zinc (Zn), and the composition ratio is In addition, elements other than In, Ga, and Zn may be contained. It is preferable to have an excess of oxygen relative to the stoichiometric ratio of the metal oxide film. This makes it possible to suppress the generation of carriers due to oxygen deficiency in the metal oxide film.

[0084] When an In-Ga-Zn-O-based material is used as the material for the metal oxide film 106, As an example of the composition of In2O3:Ga2O3:ZnO=1:1:1 [molar ratio] Furthermore, there are those with a ratio of In2O3:Ga2O3:ZnO=1:1:2 [mol A target with a composition ratio of In2O3:Ga2O3:ZnO=1:1:4 [m or a target having a composition ratio of In2O3:Ga2O3:ZnO=2: A target having a composition ratio of 1:8 [molar ratio] can also be used.

[0085] Alternatively, when an In—Zn—O-based material is used as the material for the metal oxide film 106, the number of atoms is The ratio of In:Zn is 0.5 to 50:1, preferably In:Zn is 1 to 20: 1, and more preferably In:Zn=3 to 30:2. By setting the content of the SiO 2 - ... When the atomic ratio of the compound is In:Zn:O=X:Y:Z, Z>1.5X+Y. This is preferable.

[0086] The metal oxide film 106 is formed of InMO3(ZnO) m Materials expressed as (m>0) Here, M is one or more selected from Ga, Al, Mn and Co. For example, M can be Ga, Ga and Al, Ga and Mn, or G a and Co may also be used.

[0087] The metal oxide film 106 is formed by a method such as sputtering, molecular beam epitaxy, atomic layer deposition, or The metal oxide film 106 can be formed by pulsed laser deposition. The thickness is 5 nm or more and 100 nm or less, preferably 10 nm or more and 30 nm or less. The metal oxide film is a semiconductor immediately after being formed.

[0088] The metal oxide film 106 may be amorphous or crystalline. For example, the metal oxide film 106 is non-single crystal, and more specifically, the direction perpendicular to the ab plane of the non-single crystal is When viewed from the front, the atomic arrangement is triangular, hexagonal, equilateral triangular, or equilateral hexagonal, and the c-axis is When viewed from the vertical direction, it contains a phase in which metal atoms are arranged in layers, or metal atoms and oxygen atoms are arranged in layers. In this specification, the metal oxide film is referred to as a CAAC-OS film. In addition, a CAAC-OS film is used as a film including a channel formation region of the transistor 200. This prevents damage caused by irradiation with visible or ultraviolet light, heat, bias, etc. This can suppress fluctuations in the electrical characteristics of the transistor 200 and improve the reliability of the semiconductor device. do.

[0089] There are, for example, the following two methods for forming the metal oxide film 106 into a CAAC-OS film. One method is to form the metal oxide film 106 while heating the substrate. One method is to separate the deposition of the metal oxide film 106 into two steps, and then deposit the first film and the second film. This method involves performing a heat treatment on each of the films.

[0090] When the metal oxide film 106 is formed in one step while the substrate is heated, the substrate temperature is, for example, For example, the substrate temperature is 150°C or higher and 450°C or lower, preferably 250°C or higher and 350°C or lower. In addition, when the metal oxide film 106 is formed, by increasing the temperature to which the substrate 100 is heated, A CAAC-OS film can be obtained in which the ratio of crystalline portions to amorphous portions is high. .

[0091] In addition, when the metal oxide film 106 is formed in two steps, the substrate 100 is heated to a temperature of 100 While maintaining the temperature at 450°C or higher, a first metal oxide film is formed on the gate insulating film 104. The substrate is then heated to 550°C or higher in an atmosphere of nitrogen, oxygen, rare gas, or dry air, and the strain point of the substrate is not reached. By this heat treatment, a crystalline region is formed in the region including the surface of the first metal oxide film. The second metal oxide film is then formed on the first metal oxide film. Then, heat treatment is again performed at a temperature above 550°C and below the distortion point of the substrate. The first layer of metal oxide film is formed with a crystalline region (including plate-like crystals) in the region including the surface. This acts as a seed for crystal growth, causing crystals to grow upward, crystallizing the entire second metal oxide film. Note that the first oxide semiconductor film is preferably formed to a thickness of 1 nm to 10 nm.

[0092] When the metal oxide film 106 is formed by sputtering, the metal oxide film 106 is preferably formed as thin as possible. It is preferable to reduce the hydrogen concentration contained in 106. The atmospheric gas supplied to the processing chamber of the sputtering device is a compound containing hydrogen, water, and a hydroxyl group. High-purity rare gas (typically argon) from which impurities such as nitrates or hydrides have been removed, A mixed gas of rare gas and oxygen is used as appropriate. It combines a cryopump with high pumping capacity and a sputter ion pump with high hydrogen pumping capacity. They can be used together.

[0093] By doing as described above, it is possible to form the metal oxide film 106 with reduced hydrogen contamination. Even if the above sputtering apparatus is used, the metal oxide film 106 may have some defects. It is formed by containing nitrogen. For example, secondary ion mass spectrometry (SIMS) of metal oxide film 106 measured by y Ion Mass Spectrometry The nitrogen concentration is 5 x 10 18 cm -3 It will be less than.

[0094] During or after the formation of the metal oxide film 106, oxygen deficiency in the metal oxide film 106 Generally, oxygen vacancies in metal oxide films occur when the oxygen Some of the defects become donors and generate electrons as carriers. In this case, some of the oxygen vacancies in the metal oxide film 106 become donors, and electrons, which are carriers, This causes the threshold voltage of the transistor 200 to shift in the negative direction. In the metal oxide film 106, the electrons are generated by the metal oxide film 106 and the gate insulating film. This is particularly noticeable in the oxygen vacancies occurring near the interface with the film 104 .

[0095] Therefore, after the metal oxide film 106 is formed, a first heat treatment is performed.

[0096] The first heat treatment is performed to release hydrogen (water, compounds containing hydroxyl groups) from the metal oxide film. That is, the first heat treatment removes hydrogen, which is an unstable carrier source, from the metal oxide film 106. By removing the ions, the threshold voltage of the transistor 200 shifts in the negative direction. Furthermore, the reliability of the transistor 200 can be improved. This can be done.

[0097] The temperature of the first heat treatment is, for example, 150° C. or higher and lower than the substrate strain point temperature, preferably 250° C. and 450°C or less, more preferably 300°C or more and 450°C or less, and The process is carried out in an inert atmosphere. Here, the oxidizing atmosphere is an oxidizing atmosphere such as oxygen, ozone, or oxynitride. An inert atmosphere is an atmosphere containing oxidizing gases at a concentration of 10 ppm or more. The atmosphere is filled with nitrogen or rare gases and contains less than 10 ppm of gas. The heat treatment time is 3 minutes to 24 hours. Heat treatment for more than 24 hours is not preferred because it reduces productivity. Not likely.

[0098] There is no particular limitation on the heating device used for the first heat treatment. The apparatus may be provided with a device for heating the object to be treated by induction or heat radiation. For example, an electric furnace , LRTA (Lamp Rapid Thermal Anneal) equipment, GRTA RTA (Rapid Thermal Anneal) equipment, etc. The LRTA device can be used with a halogen-free Lamps, metal halide lamps, xenon arc lamps, carbon arc lamps, high-pressure na The radiation of light (electromagnetic waves) emitted from lamps such as thorium lamps and high-pressure mercury lamps can cause The GRTA device is a device that heats the material being treated. It uses high-temperature gas to perform heat treatment. be.

[0099] Next, a resist mask is formed on the metal oxide film 106 by a photolithography process. The metal oxide film 106 is etched into a desired shape using the resist mask, and island-shaped metal A metal oxide film 106a is formed (see FIG. 3(C)). In addition to the lithography process, an ink jet method, a printing method, etc. can be used as appropriate. The etching is performed so that the edge of the metal oxide film 106a has a tapered shape. By forming the end portions of the island-shaped metal oxide films 106a into a tapered shape, it is possible to In manufacturing the transistor 200, the coverage of the formed film can be improved. The tapered shape allows the resist mask to be recessed while the etching is being performed. It can be formed by etching.

[0100] The etching process may be dry etching or wet etching. The etching solution used for wet etching is phosphoric acid. A solution of acetic acid and nitric acid, ammonia hydrogen peroxide (31% by weight hydrogen peroxide solution, 28% by weight ammonium peroxide solution), A 5:2:2 (volume ratio) of ammonium hydroxide and water can be used. N (manufactured by Kanto Chemical Co., Ltd.) may also be used.

[0101] The etching gas used in dry etching is a gas containing chlorine (chlorine-based gas, for example For example, chlorine (Cl2), boron trichloride (BCl3), silicon tetrachloride (SiCl4), carbon tetrachloride ( CCl4) is preferred. Also, a gas containing fluorine (a fluorine-based gas, for example, carbon tetrafluoride) is preferred. Fluorine (CF4), sulfur hexafluoride (SF6), nitrogen trifluoride (NF3), trifluoromethane (C HF3), hydrogen bromide (HBr), oxygen (O2), and helium (He) in these gases or a gas to which a rare gas such as argon (Ar) is added.

[0102] As dry etching, parallel plate type RIE (Reactive Ion Etching) ng) method and ICP (Inductively Coupled Plasma) The etching method (combined plasma etching) can be used. Etching conditions (amount of power applied to the coil-type electrode, amount of power applied to the substrate-side electrode, The temperature of the electrode on the substrate side, etc., is adjusted appropriately.

[0103] Next, a conductive film applicable to a source electrode and a drain electrode is formed on the metal oxide film 106a. After that, a resist mask is formed on the conductive film by a photolithography process. The conductive film is etched into a desired shape using a mask to form a source electrode or a drain electrode 1. The source electrode 108a and the drain electrode 108b are formed (see FIG. 3(D)). The conductive materials applicable to the gate electrode 102 are the same as those applicable to the gate electrode 108b. The following conductive materials can be used.

[0104] In this embodiment, the source electrode and the drain electrode 108a and 108b are formed by sputtering. By the etching method, a titanium film with a thickness of 50 nm, an aluminum film with a thickness of 100 nm, and a After forming a titanium film of 1000 nm, a photolithography process and an etching process are performed. It is formed.

[0105] Next, a pad is formed on the metal oxide film 106a and the source or drain electrodes 108a and 108b. In this embodiment, a passivation film 110 is formed (see FIG. 3(E)). As the insulating film 110, an insulating film 112, a metal oxide film 114, and an insulating film 116 are formed in this order. .

[0106] The insulating film 112 and the insulating film 116 are made of silicon oxide, gallium oxide, or aluminum oxide. An insulating film selected from silicon, silicon oxynitride, aluminum oxynitride, etc. can be used. The insulating film 112 and the insulating film 116 can be formed by the same method as the gate insulating film 104. The film forming method described above may be applied.

[0107] The metal oxide film 114 can be formed using the same material and film-forming method as the metal oxide film 106. Therefore, detailed explanation will be omitted.

[0108] The thickness of the passivation film 110 is 50 nm or more and 1000 nm or less, preferably 100 The thickness may be set to 300 nm or more.

[0109] In this embodiment, the insulating film 112 is formed by sputtering an acid film having a thickness of 200 nm. A silicon dioxide film was formed as the metal oxide film 114 by sputtering to a thickness of 5 nm. An In-Ga-Zn-O metal oxide film was formed as the insulating film 116 with a thickness of 50 A silicon oxide film is formed by sputtering at 300 nm.

[0110] When the insulating film 112 and the insulating film 116 are formed by sputtering, As long as the concentration of hydrogen contained in the insulating film 112 and the insulating film 116 is low, it is preferable to reduce the concentration of hydrogen contained in the insulating film 112 and the insulating film 116. To reduce the concentration, water is used as the atmospheric gas supplied into the processing chamber of the sputtering device. High-purity rare gas (typically Al) from which impurities such as hydrogen, water, and compounds containing hydroxyl groups have been removed. Gases such as argon, oxygen, and mixtures of rare gases and oxygen are used appropriately. The gas is generated by a cryopump with high pumping capacity for water and a sputter ion pump with high pumping capacity for hydrogen. A combination of pumps may be used.

[0111] During the first heat treatment, hydrogen is released from the metal oxide film 106a and the metal oxide film 1 There is a risk that oxygen may escape from the top surface of O6a to the outside. Oxygen vacancies may occur in the film 106a. Therefore, it is preferable to perform a second heat treatment after forming the passivation film 110.

[0112] The conditions and equipment for the second heat treatment can be the same as those for the first heat treatment, Detailed explanation will be omitted.

[0113] By performing the second heat treatment, oxygen is released from the insulating film 112, and the metal oxide film 106a On the insulating film 112, a metal oxide film is provided to prevent outward diffusion of oxygen. Since the insulating film 114 is provided, oxygen contained in the insulating film 112 is evaporated outward during the second heat treatment. Diffusion can be prevented, and oxygen can be efficiently supplied to the metal oxide film 106a. The metal oxide film 114 receives oxygen from the insulating films 112 and 116. By doing so, the resistance increases as the oxygen deficiency is compensated, and the material becomes an insulator (insulating As a result, the metal oxide film 114 is used as a part of the passivation film 110. Even if the temperature is high, the electrical characteristics of the transistor 200 are not affected.

[0114] By performing the first heat treatment and the second heat treatment, the metal oxide film 106a and the metal oxide film 106b are formed. The hydrogen concentration in the metal film 114 is reduced, and the metal film 114 becomes a highly purified metal oxide. The hydrogen concentration of the oxide film 106a and the metal oxide film 114 is 1×10 20 atoms / cm 3 Less than 1 × 10 19atoms / cm 3 Less than or equal to 1×10 18 atoms / cm 3 In addition, metal oxides are used as insulators rather than semiconductors. The hydrogen concentration of the film 114 is preferably lower. a and the hydrogen concentration in the metal oxide film 114 are measured by SIMS analysis.

[0115] The first heat treatment and the second heat treatment sufficiently reduce the hydrogen concentration and achieve high purification, and At the same time, sufficient oxygen is supplied to reduce the defect level in the energy gap caused by oxygen vacancies. The use of the metal oxide film 106a reduces the off-state current of the transistor 200. Specifically, the off-state current (here, unit channel width ( The value per 1 μm is 100 zA (1 zeptoampere is 1 × 10 -21 A) Below The current should be below 10zA, preferably below 10zA.

[0116] In addition, alkali metals such as lithium (Li) and sodium (Na) are used in the metal oxide film 10. Since the metal oxide film 6a and the metal oxide film 114 are impurities, it is preferable to reduce the content thereof. The concentration of the alkali metal contained in the metal oxide film 106a and the metal oxide film 114 is preferably , 2 × 10 16 cm -3 Less than 1 x 10, preferably 15 cm -3 It is preferable to Furthermore, since alkaline earth metals are also impurities, it is preferable to reduce their content. .

[0117] In addition, metal oxide films can be either conductive or semiconductive depending on the amount of hydrogen and oxygen vacancies. For example, the resistivity of a metal oxide film is determined by the amount of metal contained in the film. It changes depending on the amount of hydrogen and oxygen vacancies.

[0118] The insulating films sandwiching the metal oxide film are insulating films that do not release oxygen during heat treatment. When the metal oxide film is treated (for example, at 350°C), its resistivity becomes 10 Ω·cm or less. Therefore, the metal oxide film becomes a conductor. When heat treatment (for example, at 350°C) is performed using an insulating film from which oxygen is released by the chemical reaction, the resistivity is 1 x 10 8 [Ω·cm] or more, the metal oxide film becomes an insulator (showing insulating properties) Therefore, in order for the metal oxide film 114 to be an insulator, the resistivity must be 1×10 8 [ Ω·cm or more.

[0119] In order for the metal oxide film 106a to be a semiconductor, it must have a resistivity that makes it a conductor and a resistivity that makes it an insulator. Therefore, the resistivity of the metal oxide film 106a is set to 10 [Ω·cm ] beyond 1×10 8 It is sufficient to form it so that the resistivity is less than [Ω·cm].

[0120] Through the above steps, the transistor 200 can be manufactured (see FIG. 3E).

[0121] In contact with the metal oxide film (oxide semiconductor) including the channel formation region, oxygen is removed by heat treatment. An insulating film is provided to separate the insulating film from the substrate, and a metal oxide film is provided in contact with the insulating film to prevent outward diffusion of oxygen. By providing the insulating film, outward diffusion of oxygen from the insulating film is suppressed, and the metal Oxygen can be efficiently supplied to the oxide film. It is possible to reduce oxygen vacancies in the metal oxide film, thereby suppressing the generation of electrons, which act as carriers. This suppresses the negative shift of the threshold voltage of the transistor. do.

[0122] In addition, the metal oxide film for preventing outward diffusion of oxygen is an insulating film from which oxygen is released by heat treatment. The metal oxide film is sandwiched between insulating films and heat treated to prevent the outward diffusion of oxygen. Even if the temperature is low, oxygen vacancies are reduced and insulation is possible.

[0123] <Method for manufacturing an application example of a semiconductor device> The transistor 210 shown in FIG. 2A can be manufactured as follows.

[0124] After forming the gate electrode 102 on the substrate 100, the gate insulating film 120 is formed. The insulating film 120 is formed by depositing the insulating film 126, the metal oxide film 124, and the insulating film 122 in this order.

[0125] The materials and film-forming methods of the insulating films 126 and 122 are the same as those of the insulating films 116 and 112. The material and film-forming method of the metal oxide film 124 are the same as those of the metal oxide film 124. This is similar to the oxide film 114 .

[0126] Next, after the gate insulating film 120 is formed, it is preferable to perform a first heat treatment. The metal oxide film 124 is sandwiched between the insulating film 126 and the insulating film 122, from which oxygen is released by heat treatment. Since the metal oxide film 124 is covered with the metal oxide film 124, the metal oxide film 124 becomes an insulator (exhibits insulating properties). A metal oxide film is formed on the insulating film 120, and the metal oxide film is subjected to a photolithography process and An etching process is performed to form a metal oxide film 106a.

[0127] Next, a conductive film is formed on the metal oxide film 106a, and then the conductive film is subjected to photolithography. By performing the etching process and the etching process, the source electrode or the drain electrode 108a, 108 Form b.

[0128] Next, an insulating film is formed on the metal oxide film 106a and the source or drain electrodes 108a and 108b. The insulating film 118 is formed using the same material and method as the insulating film 112. After that, a second heat treatment may be performed.

[0129] In this manner, the transistor 210 can be manufactured.

[0130] The transistor 220 shown in FIG. 2B can be manufactured as follows.

[0131] After the gate electrode 102 is formed on the substrate 100, the gate insulating film 120 is formed.

[0132] Next, a metal oxide film is formed on the gate insulating film 120, and then the metal oxide film is photolithographically A metal oxide film 106a is formed by performing a lithography step and an etching step. Thereafter, a first heat treatment is performed, whereby oxygen desorbed from the insulating film 126 is converted into metal oxide. The oxygen supplied to the metal oxide film 124 and desorbed from the insulating film 122 is transferred to the metal oxide film 124 and the insulating film 122. In addition, hydrogen and water contained in the metal oxide film 106a are reduced. can be done.

[0133] Next, source and drain electrodes 108a and 108b, a photoresist, and a conductive film are formed on the metal oxide film 106a. An oxidization film 110 is formed, and then a second heat treatment is performed.

[0134] Through the above steps, the transistor 220 can be manufactured.

[0135] This embodiment mode can be implemented by being appropriately combined with the configurations described in other embodiments. is.

[0136] (Embodiment 2) In this embodiment, a transistor having a structure different from that of the transistor described in the previous embodiment is used. We will explain about this.

[0137] FIG. 4 illustrates a plan view and a schematic diagram of a transistor 400 as an example of a semiconductor device according to one embodiment of the present invention. 4(A) is a plan view, and FIG. 4(B) and FIG. 4(C) are cross-sectional views. These are cross-sectional views taken along the lines A1-A2 and B1-B2 in FIG. 4(A), in order to avoid complexity, some of the components of the transistor 400 (e.g., For example, gate insulating film 304 is omitted.

[0138] The transistor 400 shown in FIG. 4A is formed on a substrate 300 with a metal layer thereon via a base insulating film 310. A metal oxide film 306a and a source electrode or a drain electrode provided in contact with the metal oxide film 306a. The source and drain electrodes 308a and 308b, the metal oxide film 306a, and the source and drain electrodes 30 A gate insulating film 304 is provided on the gate electrodes 8a and 308b, and a metal oxide film is formed on the gate insulating film 304. and a gate electrode 302 provided so as to overlap the thin film 306a.

[0139] The substrate 300 may be the same as the substrate 100. 6a is made of the same material and formed by the same method as the metal oxide film 106a. The source or drain electrodes 308a and 308b may be formed by The electrodes 108a and 108b are made of the same material and formed by the same method. The gate insulating film 304 may be made of the same material and in the same manner as the gate insulating film 104. The gate electrode 302 may be formed by the same method as the gate electrode 102. The same material and method as those used in the above may be used.

[0140] The transistor 400 shown in FIG. 4 is a transistor with a top gate structure. The source or drain electrodes 308a and 308b are in contact with the upper surface of the metal oxide film 306a. The source and drain electrodes 308a and 308b are It may have a bottom contact structure in contact with the lower surface of the metal oxide film 306a.

[0141] The region where the metal oxide film 306a and the gate electrode 302 overlap is a channel formation region. It works like this.

[0142] An underlying insulating film 310 is provided on the substrate 300. The underlying insulating film 310 is made of gold. The metal oxide film 306a is provided so as to be in contact with the metal oxide film 306a. The base insulating film 310 includes an insulating film 312, a metal oxide film 314, and an insulating film 316. Here, the insulating films 312 and 316 are insulating films from which oxygen is released by heat treatment. The gate insulating film 304 is made of a material that does not release oxygen during heat treatment. An insulating film is used.

[0143] The metal oxide film 306 a is provided between the gate insulating film 304 and the insulating film 312 . The insulating film 312 is an insulating film from which oxygen is released by heat treatment. As a result, oxygen is released from the insulating film 312 and supplied to the metal oxide film 306a.

[0144] In one embodiment of the present invention, in addition to oxygen, a film is formed in contact with the insulating film 312 from which oxygen is released by heat treatment. A metal oxide film 314 is provided to prevent unilateral diffusion. This can prevent oxygen contained in the insulating film 312 from being released and diffusing outward.

[0145] Furthermore, in one embodiment of the present invention, the metal oxide film 31 provided to prevent outward diffusion of oxygen 4 is sandwiched between insulating films 312 and 316 from which oxygen is released by heat treatment. As a result, oxygen is released from the insulating film 316 during the heat treatment and is supplied to the metal oxide film 314. The metal oxide film 314 is supplied with oxygen from the insulating films 312 and 316. This compensates for the oxygen deficiency and makes the material an insulator (exhibits insulating properties). Even when the oxide film 314 is used as a part of the base insulating film 310, This does not affect the electrical characteristics of the capacitor 400.

[0146] In order to efficiently supply oxygen to the metal oxide film 306a, The insulating film 312 in contact with the metal oxide film 314 is preferably thicker than the insulating film 316 in contact with the metal oxide film 314. The thicknesses of the insulating films 312 and 316 are appropriately set depending on the thickness of the base insulating film 310. Just do that.

[0147] The insulating film 312 is formed from the same material and by the same method as the insulating film 112. The metal oxide film 314 may be made of the same material as the metal oxide film 114. The insulating film 316 may be formed by the same method as the insulating film 116. The same material and the same method may be used.

[0148] By using a film from which oxygen is released by heat treatment as the insulating film 312, Oxygen is supplied to the metal oxide film 306a, and the interface between the insulating film 312 and the metal oxide film 306a is formed. Therefore, the charge generated due to the operation of the transistor 400 can be reduced. This can prevent the metal oxide film 306a from being trapped at the interface between the insulating film 312 and the metal oxide film 306a. The transistor 400 can be one with little deterioration in electrical characteristics.

[0149] The metal oxide film 314 is made of In, Ga, Sn, and Zn, similarly to the metal oxide film 306a. The metal oxide film 314 is a metal oxide containing two or more elements selected from the above. The element contained in the metal oxide film 306a may be the same as or different from the element contained in the metal oxide film 306b. For example, the metal oxide film 306a and the metal oxide film 314 may be made of In—Ga Alternatively, a Zn-O-based material may be used as the metal oxide film 306a. As the metal oxide film 314, an In-Ga-Zn-ON material is used. It may be used.

[0150] <Application examples of semiconductor devices> 5A to 5C are cross-sectional views of transistors having different structures from the transistor 400. The structure is shown.

[0151] The transistor 410 shown in FIG. 5A includes an insulating film 31 over a substrate 300 as a base insulating film. 8, and the metal oxide film 306a on the insulating film 318 and the metal oxide film 306a are in contact with each other. The source electrode or drain electrode 308a, 308b and the metal oxide film 306a are provided. a gate insulating film 320 provided on the source or drain electrodes 308a and 308b; The metal oxide film 306a is provided on the gate insulating film 320 so as to overlap with the channel forming region of the metal oxide film 306a. and a gate electrode 302 formed thereon.

[0152] The difference between the transistor 400 and the transistor 410 is that the gate insulating film 320 has a The metal oxide film is provided to prevent outward diffusion of oxygen. The insulating film 320 has a three-layer structure consisting of an insulating film 322, a metal oxide film 324, and an insulating film 326. In addition, an insulating film 318 is provided as a base insulating film. , 322 and the insulating film 318 are made of an insulating film from which oxygen is released by heat treatment.

[0153] In order to efficiently supply oxygen to the metal oxide film 306a, The insulating film 322 in contact with the metal oxide film 324 is preferably thicker than the insulating film 326 in contact with the metal oxide film 324. The thicknesses of the insulating films 322 and 326 are appropriately set depending on the thickness of the gate insulating film 320. In addition, if the metal oxide film 324 is at least 5 nm thick, oxygen can pass through it. Therefore, it is only necessary to set it appropriately according to the film thickness of the gate insulating film 320.

[0154] The transistor 420 shown in FIG. 5B is formed over a substrate 300 with a gold layer therebetween and a base insulating film 310 interposed therebetween. A metal oxide film 306a and a source electrode or a drain electrode provided in contact with the metal oxide film 306a. The source and drain electrodes 308a and 308b, the metal oxide film 306a, and the source and drain electrodes 30 A gate insulating film 320 is provided on the gate electrodes 8a and 308b, and a metal oxide film is formed on the gate insulating film 320. a gate electrode 302 provided so as to overlap with a channel forming region of the semiconductor film 306a; do.

[0155] In the transistor 420, the base insulating film 310 and the gate insulating film 320 are The description of the transistor 400 and the transistor 410 can be taken into consideration, so a detailed description will be given. The clarification is omitted.

[0156] In addition, in the transistor 400, the transistor 410, and the transistor 420, The source and drain electrodes 308a and 308b are in contact with the upper surface of the metal oxide film 306a. The top contact structure has been described. The source or drain electrodes 308a and 308b are in contact with the bottom surface of the metal oxide film 306a. A top-contact structure can also be adopted. An example of a bottom-contact structure is shown in Figure 5(C). Shown below.

[0157] The transistor 430 shown in FIG. 5C includes a base insulating film 310 provided over the substrate 300. and source and drain electrodes 308a and 308b provided on the base insulating film 310. , the metal oxide film 30 provided in contact with the source electrode or drain electrode 308a, 308b. 6a, the source or drain electrodes 308a, 308b, and the metal oxide film 306a. The gate insulating film 304 is provided in a region overlapping with the channel formation region of the metal oxide film 306a. and a gate electrode 302 provided so as to contact the gate electrode 302 .

[0158] As described above, a transistor according to one embodiment of the present invention can be implemented in various forms. do.

[0159] The structures, methods, etc. described in this embodiment may be applied to structures, methods, etc. described in other embodiments. They can be used in any suitable combination.

[0160] (Embodiment 3) In this embodiment, a semiconductor device using the transistor described in the above embodiment and a manufacturing method thereof will be described. Examples of the method, as well as circuit configurations and operations, will be described with reference to Figures 6 to 8. In this embodiment, a so-called DRAM (Dynamic Random Access Memory) An example of a semiconductor device having a structure equivalent to a memory (RAM) will be described. In this case, the symbol OS is used to indicate that the transistor is formed using an oxide semiconductor. It may be attached together.

[0161] <Cross-sectional structure of semiconductor device> First, an example of a cross-sectional structure of a semiconductor device will be described with reference to FIG. The semiconductor device shown in FIG. 1A includes a transistor 400 and a capacitor 402.

[0162] A transistor 400 in FIG. 6A is a transistor according to one embodiment of the present invention. The transistor 400 is formed on a substrate 300 with a metal oxide film 310 interposed therebetween. 306a, source or drain electrodes 308a, 308b, and a gate insulating film 304. The base insulating film 310 includes an insulating film 312 and a metal oxide The insulating film 314 and the insulating film 316 are provided.

[0163] The capacitor 402 in FIG. 6A includes a gate insulating film 304, a source electrode, a drain electrode, and a The source electrode or drain electrode 308a is a capacitor. The electrode 302b functions as one electrode of the capacitor 402. It functions as such.

[0164] In addition, an insulating film 330 is provided to cover the transistor 400 and the capacitor 402. Then, the source electrode or the drain electrode 30 is formed through an opening provided in the insulating film 330. 8b and the wiring 332 are connected.

[0165] <Basic circuit> Next, the basic circuit configuration and operation of the semiconductor device shown in FIG. 6A will be described with reference to FIG. In the semiconductor device shown in FIG. 6B, the first wiring (1st Line) and the source electrode or the drain electrode of the transistor 400 are electrically connected. The second wiring (2nd Line) and the gate electrode of the transistor 400 are electrically connected 402 and the drain electrode or source electrode of the transistor 400. The source electrode is electrically connected to the third wiring (3rd Line). The other electrode of the element 402 is electrically connected.

[0166] Here, the transistor 400 is, for example, a transistor including an oxide semiconductor. A transistor including an oxide semiconductor has an extremely low off-state current. Therefore, when the transistor 400 is turned off, the The applied potential can be maintained for a very long time.

[0167] The semiconductor device shown in FIG. 6B has a feature that a potential applied to the capacitor 402 can be held. By utilizing this characteristic, it is possible to write, store, and read information as follows.

[0168] Next, we will explain how to write and store information. For simplicity, we will use the third wiring. The potential of the second wiring is fixed. The transistor 400 is turned on by applying a potential to the first transistor 400. The potential of the line is applied to one of the electrodes of the capacitor 402. Then, a predetermined charge is applied (written). Then, the potential of the second wiring is applied to the transistor 4 00 is set to a potential at which the transistor 400 is turned off, The charge applied to the capacitor 402 is held (held). Since the off-state current is extremely small, the charge can be retained for a long period of time.

[0169] Next, the reading of information will be described. In this state, when the potential of the second wiring is set to a potential that turns on the transistor 400, the capacitance element The first wiring has a different potential depending on the amount of charge held in the capacitor 402. By detecting the potential of the first wiring, the stored data can be read out.

[0170] Next, the rewriting of information will be described. That is, the potential of the second wiring is held in the same manner as when the transistor 400 is turned on. This turns on the transistor 400. (a potential related to new data) is applied to one electrode of the capacitor 402. The potential of the wiring is set to a potential at which the transistor 400 is turned off. By turning off the capacitor 402, the capacitor 402 is turned on in a state where a charge related to new data is given. It becomes a state.

[0171] In this way, the semiconductor device according to one embodiment of the present invention can directly write data by writing data again. This allows the semiconductor device to operate at high speed.

[0172] The above explanation applies to n-type transistors (n-channel transistors) that use electrons as carriers. ) is used, but instead of an n-type transistor, a It goes without saying that a p-type transistor can be used.

[0173] FIG. 7 shows an example of a circuit diagram of a semiconductor device having (m×n) memory cells 450. The configuration of the memory cell 450 in FIG. 7 is the same as that in FIG. 6. 6 corresponds to the bit line BL in FIG. 7, and the second wiring in FIG. 6 corresponds to the word line BL in FIG. 6 corresponds to the line WL, and the third wiring in FIG. 6 corresponds to the source line SL in FIG. 7 (FIG. 7 reference).

[0174] The semiconductor device shown in FIG. 7 includes n bit lines BL, m word lines WL, and memory cells 4 50 is a memory cell array arranged in a matrix of m rows x n columns, and n a first driver circuit 461 connected to m bit lines BL, and a second driver circuit 462 connected to m word lines WL. and two drive circuits 462.

[0175] The memory cell 450 includes a transistor 400 and a capacitor 402 . The gate electrode of the transistor 400 is connected to the word line WL. One of the source electrode or the drain electrode of the transistor 400 is connected to the bit line BL. The other of the source electrode and the drain electrode of the transistor 400 is connected to one of the electrodes of the capacitor 402. The other electrode of the capacitor 402 is connected to the source line SL. The transistor 400 has the same structure as the transistor shown in the previous embodiment. The data applies.

[0176] A semiconductor device according to one embodiment of the present invention includes a transistor including an oxide semiconductor in a channel formation region. Therefore, compared to transistors using single crystal silicon for the channel formation region, It has the characteristic of small current. For this reason, it is recognized as a so-called DRAM. When the transistor is applied to the semiconductor device shown in FIG. 7, the refresh period can be extremely long. It is possible to obtain a large memory.

[0177] <Method for manufacturing semiconductor device> Next, a manufacturing method of the semiconductor device shown in FIG. 6 will be described with reference to FIG.

[0178] First, an insulating film 312 that functions as a base insulating film 310 and a metal oxide film 3 14, and an insulating film 316 are formed in this order (see FIG. 8(A)). Since the same materials as those of the insulating film 312 and the insulating film 313 can be used, detailed explanations are omitted. The insulating film 316 can be obtained by referring to the description of the insulating film 112 and the insulating film 116, respectively. do.

[0179] Next, a metal oxide film 306a is formed over the base insulating film 310 (see FIG. 8B). For the metal oxide film 306a, the description of the metal oxide film 106a can be referred to.

[0180] Next, the source and drain electrodes 308a and 308b in contact with the metal oxide film 306a are After the formation, the metal oxide film 306a is formed on the source electrode or drain electrode 308a, 308b. Then, a gate insulating film 304 is formed on the gate insulating film 304. Then, a metal oxide film 30 A gate electrode 302a is formed in the region overlapping with the channel forming region of 6a, and a source The electrode 302b is formed in a region overlapping with the drain electrode 308a (see FIG. 8C). The source or drain electrodes 308a and 308b are The descriptions in 108a and 108b can be taken into consideration.

[0181] Next, an interlayer insulating film is formed to cover the gate insulating film 304, the gate electrode 302a, and the electrode 302b. Then, the insulating film 330 and the gate insulating film 3 An opening is formed in the insulating film 330, and a wiring 332 is formed on the insulating film 330. The rain electrode 308b and the wiring 332 are electrically connected.

[0182] The insulating film 330, which functions as an interlayer insulating film, is made of an inorganic material (silicon oxide, silicon nitride, etc.). , silicon oxynitride, etc.), photosensitive or non-photosensitive organic materials (polyimide, acrylic, polyimide, etc.), polyimide, polyimide amide, resist or benzocyclobutene), silicon (Si) and oxygen The skeleton structure is formed by bonding with (O), and the substituent contains at least hydrogen or the substituent contains fluorine. Materials containing at least one of fluorine, alkyl groups, and aromatic hydrocarbons, so-called silicon Polyoxanes and their laminated structures can be used.

[0183] The wiring 332 is formed by depositing a conductive film using a sputtering method, a plasma CVD method, or the like. Then, the conductive film is subjected to a photolithography process and an etching process. The conductive film is made of aluminum, chromium, copper, tantalum, titanium, molybdenum, etc. It is possible to use an element selected from the group consisting of tungsten and tungsten, or an alloy containing the above-mentioned elements. Manganese, magnesium, zirconium, beryllium, neodymium, scandium The gate electrode may be made of any one of the above materials or a combination of these materials. It is similar to 102.

[0184] Through the above steps, a semiconductor device including the transistor 400 and the capacitor 402 is manufactured. This can be done (see FIG. 8(D)).

[0185] As described above, the configurations, methods, etc. shown in this embodiment may be applied to the configurations, methods, etc. shown in other embodiments. They can be used in any suitable combination.

[0186] (Fourth embodiment) A semiconductor device according to one embodiment of the present invention can be applied to various electronic devices (including gaming machines). The electronic device can be, for example, a television device (television or television (also called digital receivers), computer monitors, digital cameras, digital video cameras cameras such as digital cameras, digital photo frames, mobile phones (also called mobile phones or mobile phone devices) (c), portable game machines, personal digital assistants, audio playback devices, large game machines such as pachinko machines, etc. Examples of electronic devices including the semiconductor device described in the above embodiments include: explain.

[0187] FIG. 9A shows a notebook personal computer, which includes a main body 3001 and a housing 3002. , a display unit 3003, a keyboard 3004, etc. The semiconductor device shown in Embodiment 2 can be applied to the display portion 3003. The semiconductor device can be applied to a memory circuit included inside the housing 3002. The semiconductor devices according to the first to third embodiments have high reliability because fluctuations in electrical characteristics are suppressed. The computer may be a high performance notebook computer.

[0188] FIG. 9B shows a personal digital assistant (PDA), and a main body 3021 includes a display unit 3023 and an external An external interface 3025 and operation buttons 3024 are also provided. The stylus 3022 is an accessory. The semiconductor device shown in Embodiment 3 can be applied to the main body 302. The present invention can be applied to the memory circuit included in the semiconductor device according to the first to third embodiments. The device is a highly reliable personal digital assistant (PDA) because the fluctuation of electrical characteristics is suppressed. ) can be used.

[0189] 9C shows an example of an electronic book. For example, the electronic book has a housing 2701 and The housing 2701 and the housing 2703 are made up of two housings. The shaft 2711 serves as an axis for opening and closing. This configuration allows the device to operate like a paper book.

[0190] A display unit 2705 is incorporated in the housing 2701, and a display unit 2707 is incorporated in the housing 2703. The display unit 2705 and the display unit 2707 are configured to display a continuous screen. Alternatively, a different screen may be displayed. For example, a sentence is displayed on the right display unit (display unit 2705 in FIG. 9C), and a An image can be displayed on the display unit (display unit 2707 in FIG. 9C). The semiconductor device shown in FIG. 2 can be applied to the display portion 2705 and the display portion 2707. The semiconductor device described in Embodiment 3 is a memory circuit included in the housings 2701 and 2703. The semiconductor devices according to the first to third embodiments can be applied to circuits that are free from fluctuations in electrical characteristics. Since the amount of information read is suppressed, the electronic book can be made highly reliable.

[0191] FIG. 9C shows an example in which an operation unit and the like are provided on the housing 2701. The body 2701 includes a power supply 2721, operation keys 2723, a speaker 2725, etc. The operation keys 2723 can be used to turn pages. The back of the housing may be provided with a keyboard, a pointing device, etc. On the front and sides, there are external connection terminals (earphone terminal, USB terminal, etc.), a recording medium insertion port, etc. Furthermore, the electronic book may be configured to have a function as an electronic dictionary. You may do so.

[0192] The electronic book may also be configured to be capable of transmitting and receiving information wirelessly. It is also possible to purchase and download desired book data from the server. be.

[0193] FIG. 9(D) shows a mobile phone, which is composed of two housings, a housing 2800 and a housing 2801. The housing 2801 contains a display panel 2802, a speaker 2803, a microphone, and a 2804, pointing device 2806, camera lens 2807, external connection terminal 2 808, etc. The housing 2800 also includes a solar cell for charging the mobile phone. 2810, an external memory slot 2811, etc. The antenna is mounted on the housing 280 The semiconductor device shown in Embodiments 1 and 2 is incorporated in the display panel 2802. The semiconductor device shown in the third embodiment can be applied to the housings 2800 and 280 The present invention can be applied to the memory circuit included in the semiconductor device according to the first to third embodiments. The device has suppressed fluctuations in electrical characteristics, making it a highly reliable mobile phone. can.

[0194] The display panel 2802 is equipped with a touch panel, and in FIG. 9(D) an image is displayed. The multiple operation keys 2805 are indicated by dotted lines. A boost circuit is also implemented to boost the voltage required for each circuit.

[0195] The display direction of the display panel 2802 changes appropriately depending on the usage mode. The camera lens 2807 is located on the same surface as the camera lens 2802, so video calls are possible. The speaker 2803 and microphone 2804 are not limited to voice calls, but also to video calls, Recording and playback are possible. Furthermore, the housing 2800 and the housing 2801 can be slid apart. It can be folded from the unfolded state as shown in 9(D) to the overlapping state, making it suitable for carrying. It is possible to make the device smaller.

[0196] The external connection terminal 2808 can be connected to various cables such as AC adapters and USB cables. It is possible to charge the battery and to communicate data with a personal computer, etc. By inserting a recording medium into the memory slot 2811, it is possible to store and transfer a larger amount of data. do.

[0197] In addition to the above functions, even if the device has infrared communication function, TV reception function, etc. good.

[0198] FIG. 9(E) shows a digital video camera, which includes a main body 3051, a display unit (A) 3057, and a connection Eye part 3053, operation switch 3054, display part (B) 3055, battery 3056, etc. The semiconductor device shown in the first and second embodiments is configured as the display portion (A) 3057. The semiconductor device shown in Embodiment 3 can be applied to the display portion (B) 3055. This can be applied to the memory circuit contained inside the main body 3051. The semiconductor device according to any one of claims 1 to 3 has suppressed fluctuations in electrical characteristics, and therefore has high reliability. It can be a portable video camera.

[0199] FIG. 9F shows an example of a television device. The television device 9600 is A display unit 9603 is built into the body 9601. The display unit 9603 displays an image. In this example, the housing 9601 is supported by a stand 9605. The semiconductor device described in Embodiments 1 and 2 can be applied to the display portion 9603. The semiconductor device described in Embodiment 3 can be mounted on a metal substrate included in the housing 9601. The semiconductor devices according to the first to third embodiments can be applied to memory circuits. Since the fluctuations in the signal level are suppressed, a highly reliable television device can be obtained.

[0200] The television device 9600 can be operated using an operation switch on the housing 9601 or a separate remote control. This can be done by a remote control operator. A display unit for displaying the output information may be provided.

[0201] The television device 9600 is configured to include a receiver, a modem, and the like. It can receive more general TV broadcasts and can also receive them via wired or wireless modems. By connecting to a communication network, it can be one-way (sender to receiver) or two-way. It is also possible to communicate information (between a sender and a receiver, or between receivers).

[0202] This embodiment mode can be implemented by being appropriately combined with the configurations described in other embodiments. is. [Example]

[0203] In this example, a MOS (Metal Oxide Semiconductor) substrate The breakdown voltage and CV (Capacitance-Voltage) measurements were carried out. The results will be explained with reference to FIGS.

[0204] First, a method for preparing the samples used in this example will be described.

[0205] As sample A, a first insulating film was formed on a silicon substrate by sputtering. A silicon oxide film was formed to a thickness of 50 nm. Next, a metal oxide film was formed on the silicon oxide film. Then, a 10 nm thick In-Ga-Zn-ON metal oxide was deposited by sputtering. Next, a second insulating film was formed on the In-Ga-Zn-O-N metal oxide film. As a result, a silicon oxide film was formed to a thickness of 50 nm by sputtering.

[0206] Sample B is an In-Ga-Zn-ON metal oxide film, which is the same as the metal oxide film in sample A. Instead of the metal film, a 10 nm thick In-Ga-Zn-O metal film was deposited by sputtering. The other configurations and manufacturing methods were the same as those of Sample A.

[0207] As sample C, a first insulating film was formed on a silicon substrate by plasma CVD. A silicon oxynitride film was formed to a thickness of 50 nm. Next, a sputtering method was performed on the silicon oxynitride film. A 10 nm thick In-Ga-Zn-O metal oxide film was formed by the ring method. Then, a second insulating film is formed on the In-Ga-Zn-O metal oxide film by plasma C A silicon oxynitride film was formed to a thickness of 50 nm by the VD method.

[0208] In Sample D, instead of the silicon oxide film (first insulating film and second insulating film) in Sample A, A silicon oxynitride film was formed to a thickness of 50 nm using the plasma CVD method. The fabrication method is the same as that of Sample A.

[0209] For sample E, a silicon oxide film with a thickness of 100 nm was deposited on a silicon substrate by sputtering. A coating was formed.

[0210] Next, heat treatment was performed on Samples A to E. The heat treatment conditions were a nitrogen atmosphere, temperature The heating was carried out at 300°C for 1 hour.

[0211] Next, for each of Samples A to E, a thin film was formed on the second insulating film by a sputtering method. The electrode (electrode area 0.785 mm) is made of an aluminum-titanium alloy film with a thickness of 400 nm. 2 ) was formed.

[0212] Finally, samples A to E were subjected to a heat treatment in a nitrogen atmosphere at a temperature of 250°C for 1 hour. It was.

[0213] The structures of the MOS substrates of Samples A to E obtained as described above are shown in Table 1.

[0214] [Table 1]

[0215] Next, the current-voltage (IV) characteristics of Samples A to E were measured. Measurements were taken at 13 points each.

[0216] The results of the withstand voltage measurement are shown in Figs. 10 to 12. Fig. 10(A) shows the results for sample A, and Fig. 1 11(B) shows the results for sample B, FIG. 11(A) shows the results for sample C, and FIG. 11(B) shows the results for sample B. 10 to 12, the horizontal axis represents the voltage The vertical axis indicates the voltage, and the vertical axis indicates the current.

[0217] In the sample C shown in FIG. 11(A) and the sample D shown in FIG. 11(B), the rise of the current In contrast, sample A shown in FIG. 10(A) and sample B shown in FIG. 10(B) were In sample B shown in (B), the current rise is slower than in samples C and D. Furthermore, sample E shown in FIG. 12 has the same breakdown voltage as samples A and B. It was found that the material had pressure resistance.

[0218] Next, CV measurements were carried out on Samples A to E. Four measurements were carried out on each sample. went.

[0219] The results of the CV measurement are shown in Figs. 13 to 15. Fig. 13(A) shows the results for sample A, and Fig. 13(B) shows the results for sample B, FIG. 14(A) shows the results for sample C, and FIG. 14(B) shows the results for sample D, and FIG. 15 shows the results for sample E. In FIGS. 13 to 15, the horizontal axis indicates voltage, and the vertical axis indicates capacitance value.

[0220] For sample C shown in Figure 14(A) and sample D shown in Figure 14(B), CV curves were obtained. As can be seen from the results in Figure 11, this was not possible with specimens C and D. This is thought to be because the dielectric strength of the insulating film was insufficient and the capacitance could not be maintained. In contrast, sample A shown in FIG. 13(A), sample B shown in FIG. 13(B), and sample C shown in FIG. In the case of sample E, a good CV curve was obtained.

[0221] Furthermore, the CV curves of samples A and B are positively charged compared to the CV curve of sample E. This is because the negative shift in samples A and B was observed compared to sample E. This is because there are many fixed charges. By forming the metal oxide film including the metal oxide film in contact with the metal oxide film, the threshold voltage of the transistor can be reduced. It was suggested that the value of the α-saturation potential can be shifted in a positive direction.

[0222] Samples C and D are made of an insulating film sandwiching a metal oxide film and a nitride oxide film formed by plasma CVD. Silicon oxynitride film is used. In this case, there is no oxygen desorption due to heat treatment. Therefore, oxygen is supplied from the insulating film to the metal oxide film. It is thought that the metal oxide film could not be insulated. The insulating films sandwiching the metal oxide film are made of silicon oxide films formed by sputtering. The silicon oxide film formed by sputtering loses oxygen when heat treated, It is believed that sufficient oxygen was supplied to the metal oxide film, making it insulating. This is thought to be the reason why the breakdown voltage of Samples A and B has improved.

[0223] From the above results, when a metal oxide film is provided between insulating films from which oxygen is released by heat treatment, It was shown that the metal oxide film functions as an insulating film. [Example]

[0224] In this example, a metal oxide film was formed on an insulating film that releases oxygen by heat treatment by TDS analysis. In the structure to be formed, the amount of oxygen that diffuses outward from the insulating film through the metal oxide film is The results of this investigation will be explained below.

[0225] First, Samples F to I used in this example will be described.

[0226] Sample F was prepared by sputtering a silicon oxide film with a thickness of 100 nm on a glass substrate. Next, a silicon oxide film was formed on the silicon oxide film by sputtering to a thickness of 5 nm. An In-Ga-Zn-O metal oxide film was formed.

[0227] As sample G, a silicon oxide film with a thickness of 100 nm was deposited on a glass substrate by sputtering. Next, a silicon oxide film having a thickness of 10 nm was formed on the silicon oxide film by sputtering. An In-Ga-Zn-O metal oxide film was formed.

[0228] Sample H was prepared by sputtering a silicon oxide film with a thickness of 100 nm on a glass substrate. Next, a silicon oxide film having a thickness of 15 nm was formed on the silicon oxide film by sputtering. An In-Ga-Zn-O metal oxide film was formed.

[0229] Sample I was prepared by sputtering a silicon oxide film with a thickness of 100 nm on a glass substrate. A film was formed.

[0230] Next, TDS analysis was performed on Samples F to I. In this example, the number of desorbed oxygen The values ​​were measured using a thermal desorption analyzer EMD-WA1000S / W manufactured by Electronic Science Corporation.

[0231] FIG. 16 shows the TDS analysis results of Samples F to I.

[0232] As shown in FIG. 16, for sample I on which only a silicon oxide film was formed, the temperature was around 200°C. In contrast, the peak was higher at the sample where a metal oxide film was formed on a silicon oxide film. For samples F to H, almost no peaks were detected.

[0233] From the results in FIG. 16, it can be seen that the formation of a metal oxide film on a silicon oxide film reduces the amount of oxidation. It was found that the oxygen contained in the silicon oxide film was not released to the outside. If the film is formed at least 5 nm thick, the oxygen contained in the silicon oxide film will not be released to the outside. These results demonstrate that metal oxide films can prevent oxygen from passing through. was done. [Example]

[0234] In this example, the resistivity of the metal oxide film was investigated. The results are shown in FIG. explain.

[0235] First, the sample used in this example will be described with reference to FIG.

[0236] (Condition 1) The insulating films sandwiching the metal oxide film 506 are made of insulating films that do not release oxygen by heat treatment. This is considered to be condition 1.

[0237] First, a 100% thick insulating film 502 was formed on a glass substrate 500 by plasma CVD. A silicon oxynitride film was formed at 0 nm.

[0238] Next, a tungsten film was formed to a thickness of 100 nm by sputtering. The tungsten film is subjected to a photolithography process and an etching process to form electrodes 504a and 504b. 04b was formed.

[0239] Next, as the metal oxide film 506, an In-Ga-Zn-O system A metal oxide film was formed under the conditions of a composition ratio of In:Ga:Zn=1:1. A 1:1 target was used, Ar / O2 = 30 / 15sccm, pressure 0.4Pa, power 0. The power was 5 kW, the substrate temperature was 200° C., and the film thickness was 30 nm. The heat treatment was carried out in an atmosphere at 450°C for 1 hour.

[0240] Next, as the insulating film 508, a silicon oxynitride film is formed to a thickness of 100 nm by the plasma CVD method. A silicon film was formed.

[0241] Next, the insulating film 508 and the metal oxide film 506 are subjected to photolithography and etching processes. By carrying out this step, openings were formed so that the electrodes 504a and 504b were exposed.

[0242] Finally, the sample was subjected to heat treatment at 350°C for 1 hour in a nitrogen atmosphere.

[0243] (Condition 2) The insulating films sandwiching the metal oxide film 506 are made of insulating films that release oxygen by heat treatment. This is called condition 2.

[0244] First, a 100% thick insulating film 502 was formed on a glass substrate 500 by sputtering. A silicon oxide film was formed at 0 nm.

[0245] Next, a tungsten film was formed to a thickness of 100 nm by sputtering. The tungsten film is subjected to a photolithography process and an etching process to form electrodes 504a and 504b. 04b was formed.

[0246] Next, as the metal oxide film 506, an In-Ga-Zn-O system A metal oxide film was formed under the conditions of a composition ratio of In:Ga:Zn=1:1. A 1:1 target was used, Ar / O2 = 30 / 15sccm, pressure 0.4Pa, power 0. The power was 5 kW, the substrate temperature was 200° C., and the film thickness was 30 nm. The heat treatment was carried out in an atmosphere at 450°C for 1 hour.

[0247] Next, as the insulating film 508, a silicon oxide film is formed by sputtering to a thickness of 100 nm. A film was formed.

[0248] Next, the insulating film 508 and the metal oxide film 506 are subjected to photolithography and etching processes. By carrying out this step, openings were formed so that the electrodes 504a and 504b were exposed.

[0249] Finally, the sample was subjected to heat treatment at 350°C for 1 hour in a nitrogen atmosphere.

[0250] (Condition 3) The insulating film 502 is an insulating film from which oxygen is released by heat treatment, and the insulating film 508 is an insulating film from which oxygen is released by heat treatment. Therefore, the case where an insulating film from which oxygen is not released is used is defined as condition 3.

[0251] First, a 100% thick insulating film 502 was formed on a glass substrate 500 by sputtering. A silicon oxide film was formed at 0 nm.

[0252] Next, a tungsten film was formed to a thickness of 100 nm by sputtering. The tungsten film is subjected to a photolithography process and an etching process to form electrodes 504a and 504b. 04b was formed.

[0253] Next, as the metal oxide film 506, an In-Ga-Zn-O system A metal oxide film was formed under the conditions of a composition ratio of In:Ga:Zn=1:1. A 1:1 target was used, Ar / O2 = 30 / 15sccm, pressure 0.4Pa, power 0. The power was 5 kW, the substrate temperature was 200° C., and the film thickness was 30 nm. The heat treatment was carried out in an atmosphere at 450°C for 1 hour.

[0254] Next, as the insulating film 508, a silicon oxynitride film is formed to a thickness of 100 nm by the plasma CVD method. A silicon film was formed.

[0255] Next, the insulating film 508 and the metal oxide film 506 are subjected to photolithography and etching processes. By carrying out this step, openings were formed so that the electrodes 504a and 504b were exposed.

[0256] Finally, the sample was subjected to heat treatment at 350°C for 1 hour in a nitrogen atmosphere.

[0257] (Condition 4) The insulating film 502 is an insulating film that does not release oxygen by heat treatment, and the insulating film 508 is Condition 4 is the case where an insulating film from which oxygen is released by heat treatment is used.

[0258] First, a 100% thick insulating film 502 was formed on a glass substrate 500 by plasma CVD. A silicon oxynitride film was formed at 0 nm.

[0259] Next, a tungsten film was formed to a thickness of 100 nm by sputtering. The tungsten film is subjected to a photolithography process and an etching process to form electrodes 504a and 504b. 04b was formed.

[0260] Next, as the metal oxide film 506, an In-Ga-Zn-O system A metal oxide film was formed under the conditions of a composition ratio of In:Ga:Zn=1:1. A 1:1 target was used, Ar / O2 = 30 / 15sccm, pressure 0.4Pa, power 0. The power was 5 kW, the substrate temperature was 200° C., and the film thickness was 30 nm. The heat treatment was carried out in an atmosphere at 450°C for 1 hour.

[0261] Next, as the insulating film 508, a silicon oxide film is formed by sputtering to a thickness of 100 nm. A film was formed.

[0262] Next, the insulating film 508 and the metal oxide film 506 are subjected to photolithography and etching processes. By carrying out this step, openings were formed so that the electrodes 504a and 504b were exposed.

[0263] Finally, the sample was subjected to heat treatment at 350°C for 1 hour in a nitrogen atmosphere.

[0264] Next, the conductivity σ was measured at four points for each of the samples described under conditions 1 to 4. The resistivity ρ was calculated from the measured conductivity σ, and the average value of the four points was calculated. , as shown in Table 2.

[0265] [Table 2]

[0266] As shown in Table 2, the resistivity ρ of the metal oxide film under condition 1 is 1.4 × 10 ―2 [Ω· The resistivity ρ of the metal oxide film under condition 2 was found to be 7.4 x10 9 In addition, the resistance of the metal oxide film under condition 3 was calculated as [Ω·cm]. The rate ρ is 8.6×10 3 In addition, the metal The resistivity ρ of the oxide film is 8.5×10 6 It was possible to calculate the value as [Ω·cm].

[0267] From the results of the condition 1, the metal oxide film 506 was reduced by the heat treatment after the film formation. The resistance of 506 remains low even after heat treatment is performed after the insulating film 508 is formed. As a result, it was found that the metal oxide film 506 has conductive properties.

[0268] In addition, the results of condition 2 show that the metal oxide film 506 was reduced by heat treatment after deposition. It has been found that the resistance of the insulating film 506 increases by performing a heat treatment after the formation of the insulating film 508. This is because oxygen is supplied from the insulating film 502 and the insulating film 508 to the metal oxide film. This is thought to be because the generated oxygen vacancies are compensated for. As a result, the metal oxide film 506 It was found that the material becomes an insulator (exhibits insulating properties).

[0269] In addition, the results of conditions 3 and 4 show that the heat treatment after the formation of the insulating film 508 reduces the metal oxide The resistance of the metal oxide film 506 is higher than that of Condition 1 and lower than that of Condition 2. It was found that the oxide film 506 became a semiconductor.

[0270] From the above results, it is possible to determine the type of insulating film in contact with the metal oxide film (or the amount of oxygen released from the insulating film). It was shown that the resistance of metal oxide films can be adjusted by adjusting the amount of [Explanation of symbols]

[0271] 100 boards 102 gate electrode 104 Gate insulating film 106 Metal oxide film 106a Metal oxide film 108a Source electrode or drain electrode 108b Source electrode or drain electrode 110 Passivation film 112 insulating film 114 Metal oxide film 116 Insulating film 118 insulating film 120 Gate insulating film 122 insulating film 124 Metal oxide film 126 insulating film 200 transistors 210 Transistor 220 transistors 230 transistors 300 boards 302 Gate electrode 304 Gate insulating film 306a Metal oxide film 308a Source electrode or drain electrode 308b Source electrode or drain electrode 310 Undercoat insulating film 312 insulating film 314 Metal oxide film 316 Insulating Film 318 Insulating Film 320 Gate insulating film 322 insulating film 324 Metal oxide film 326 Insulating Film 330 Insulating Film 332 Wiring 400 transistors 402 Capacitor element 410 Transistor 420 transistors 430 transistors 450 memory cells 461 Drive Circuit 462 Drive Circuit 500 glass substrates 502 insulating film 504a electrode 504b electrode 506 Metal oxide film 508 insulating film 2701 Housing 2703 Housing 2705 ​​Display section 2707 Display section 2711 Shaft 2721 Power supply 2723 Operation Key 2725 Speaker 2800 chassis 2801 Case 2802 Display panel 2803 Speaker 2804 Microphone 2805 Operation Key 2806 Pointing Device 2807 Camera lenses 2808 External connection terminal 2810 solar cell 2811 External Memory Slot 3001 main unit 3002 Case 3003 Display section 3004 Keyboard 3021 Main Unit 3022 stylus 3023 Display section 3024 Operation button 3025 External Interface 302a Gate electrode 302b electrode 3051 Main Unit 3053 Eyepiece 3054 Operation switch 3055 Display section (B) 3056 Battery 3057 Display section (A) 9600 Television Equipment 9601 Housing 9603 Display section 9605 Stand

Claims

1. a first conductive film that functions as a gate electrode of a transistor; a first insulating film having a region disposed above the first conductive film; a first metal oxide film having a region disposed above the first insulating film and having a channel formation region of the transistor; a second conductive film having a region in contact with each of a side surface and a top surface of the first metal oxide film and functioning as one of a source electrode and a drain electrode of the transistor; a third conductive film having regions in contact with the side surface and the top surface of the first metal oxide film and functioning as the other of the source electrode and the drain electrode of the transistor; a second insulating film having a region disposed above the second conductive film, a region disposed above the third conductive film, and a region disposed above the first metal oxide film, and containing silicon oxide; a second metal oxide film having a region disposed above the second insulating film; a third insulating film having a region disposed above the second metal oxide film; the second insulating film has a region in contact with the first metal oxide film in a region between the second conductive film and the third conductive film, the first metal oxide film contains indium; the second metal oxide film contains indium; the second metal oxide film overlaps with a channel formation region of the first metal oxide film; the second metal oxide film is not in contact with the second conductive film and is not in contact with the third conductive film; a periphery of a region of the first metal oxide film that overlaps with the first conductive film and does not overlap with the second conductive film or the third conductive film overlaps with the second metal oxide film.

2. a first conductive film that functions as a gate electrode of a transistor; a first insulating film having a region disposed above the first conductive film; a first metal oxide film having a region disposed above the first insulating film and having a channel formation region of the transistor; a second conductive film having a region in contact with each of a side surface and a top surface of the first metal oxide film and functioning as one of a source electrode and a drain electrode of the transistor; a third conductive film having regions in contact with the side surface and the top surface of the first metal oxide film and functioning as the other of the source electrode and the drain electrode of the transistor; a second insulating film having a region disposed above the second conductive film, a region disposed above the third conductive film, and a region disposed above the first metal oxide film, and containing silicon oxide; a second metal oxide film having a region disposed above the second insulating film; a third insulating film having a region disposed above the second metal oxide film; the second insulating film has a region in contact with the first metal oxide film in a region between the second conductive film and the third conductive film, the first metal oxide film contains indium; the second metal oxide film contains indium; the first metal oxide film includes a phase in which metal atoms are arranged in layers or a phase in which metal atoms and oxygen atoms are arranged in layers when viewed in a direction perpendicular to the c-axis, the second metal oxide film overlaps with a channel formation region of the first metal oxide film; the second metal oxide film is not in contact with the second conductive film and is not in contact with the third conductive film; a periphery of a region of the first metal oxide film that overlaps with the first conductive film and does not overlap with the second conductive film or the third conductive film overlaps with the second metal oxide film.

3. a first conductive film that functions as a gate electrode of a transistor; a first insulating film having a region disposed above the first conductive film; a first metal oxide film having a region disposed above the first insulating film and having a channel formation region of the transistor; a second conductive film having a region in contact with each of a side surface and a top surface of the first metal oxide film and functioning as one of a source electrode and a drain electrode of the transistor; a third conductive film having regions in contact with the side surface and the top surface of the first metal oxide film and functioning as the other of the source electrode and the drain electrode of the transistor; a second insulating film having a region disposed above the second conductive film, a region disposed above the third conductive film, and a region disposed above the first metal oxide film, and containing silicon oxide; a second metal oxide film having a region disposed above the second insulating film; a third insulating film having a region disposed above the second metal oxide film; the second conductive film and the third conductive film contain a metal oxide; the second insulating film has a region in contact with the first metal oxide film in a region between the second conductive film and the third conductive film, the first metal oxide film contains indium; the second metal oxide film contains indium; the second metal oxide film overlaps with a channel formation region of the first metal oxide film; the second metal oxide film is not in contact with the second conductive film and is not in contact with the third conductive film; a periphery of a region of the first metal oxide film that overlaps with the first conductive film and does not overlap with the second conductive film or the third conductive film overlaps with the second metal oxide film.

4. a first conductive film that functions as a gate electrode of a transistor; a first insulating film having a region disposed above the first conductive film; a first metal oxide film having a region disposed above the first insulating film and having a channel formation region of the transistor; a second conductive film having a region in contact with each of a side surface and a top surface of the first metal oxide film and functioning as one of a source electrode and a drain electrode of the transistor; a third conductive film having regions in contact with the side surface and the top surface of the first metal oxide film and functioning as the other of the source electrode and the drain electrode of the transistor; a second insulating film having a region disposed above the second conductive film, a region disposed above the third conductive film, and a region disposed above the first metal oxide film, and containing silicon oxide; a second metal oxide film having a region disposed above the second insulating film; a third insulating film having a region disposed above the second metal oxide film; the second conductive film and the third conductive film contain a metal oxide; the second insulating film has a region in contact with the first metal oxide film in a region between the second conductive film and the third conductive film, the first metal oxide film contains indium; the second metal oxide film contains indium; the first metal oxide film includes a phase in which metal atoms are arranged in layers or a phase in which metal atoms and oxygen atoms are arranged in layers when viewed in a direction perpendicular to the c-axis, the second metal oxide film overlaps with a channel formation region of the first metal oxide film; the second metal oxide film is not in contact with the second conductive film and is not in contact with the third conductive film; a periphery of a region of the first metal oxide film that overlaps with the first conductive film and does not overlap with the second conductive film or the third conductive film overlaps with the second metal oxide film.

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